1. Field of the Invention
The invention relates to a system and a method for storing and shipping temperature-sensitive materials. In particular, the present invention discloses a system and method suitable for transporting temperature-sensitive products, such as human blood products and pharmaceuticals, within a predetermined temperature range, utilizing at least two temperature control materials having separate phase change temperatures which approximately bracket the target temperature range.
2. Background of the Invention
The conventional means of shipping temperature sensitive materials such as blood and blood products involves the use of an insulated box, with the necessary shipping and warning labels, along with some cooling agent. These cooling agents are typically a frozen gel, dry ice, or glistening (wet) ice.
There are, however, several problems with the conventional approach. First, the styrofoam used for insulation does not degrade readily, leading to disposal problems. These problems are so severe that many countries ban the use of styrofoam, thus severely restricting international shipments of biological materials. Second, the cooling agents also present numerous practical problems in field use. Specifically, gel systems are often too expensive for routine use and disposal. As for dry ice, the carbon dioxide gas evolved during shipment is so dangerous to shipping personnel that hazard warnings must be posted and additional fees paid; furthermore, outright bans on dry ice are pending in several areas. Finally, wet ice poses handling problems in packing, as well as leakage and product soaking problems.
Many previously existing shipping systems also suffer the disadvantage that they are not capable of maintaining the shipped product or payload within a target temperature range. Various biological products, such as platelets, whole blood, semen, organs and tissue, must be maintained above a predetermined minimum temperature and below a predetermined maximum temperature. Pharmaceutical products are also commonly required to be kept within a specified temperature range. Food products, flowers and produce frequently have preferred storage temperature ranges as well. Many known methods and systems for shipping such products are not able to keep temperatures within the desired range. For example, one company ships vaccine packed in dry ice, which sublimes at -78.6.degree. C., even through the specified temperature for storage of the vaccine is approximately -15.degree. C. The result of this practice is excessive cooling, frequently resulting in damage to the vaccine.
Previously known methods and systems which are capable of maintaining a payload within a specified temperature range have been found to be unsuited to certain applications, unduly complex in practice, and/or prohibitively expensive. For example, refrigerated containers require associated compressors, coils, crystals, or other equipment, which adds to the apparatus' expense, weight and size. Additionally, this type of equipment generally requires batteries or connection to an external power source. Refrigerated containers also require ventilation, so that heat from the payload can be rejected to the ambient. Sufficient ventilation for the proper operation of these devices is generally unavailable in the closely-packed cargo compartments of common carrier transport vehicles. Refrigerated transport vehicles exist, but are substantially more expensive than unrefrigerated transport, and are not as readily available.
Another problem often observed with conventional systems is failure to maintain the proper temperature over time, due to inadequate insulation and/or inadequate cooling pack capacity. Again, the end result is product damage.
Yet another problem commonly observed with conventional shipping systems is a strong sensitivity to infrared heat transfer. Specifically, many systems heat rapidly when left in direct sunlight. Part of this susceptibility may be due to the standard industry practice of testing shipping containers only in convective, non-radiative heating systems. While this practice may be appropriate for evaluating shaded or otherwise protected systems, test results obtained in this manner do not accurately anticipate the real world use of shipping containers left indefinitely in direct sunlight on loading docks, etc.
An additional problem is that many insulated storage boxes do not tolerate the condensation that results during conditions of high humidity. Common failures include box collapse due to the dissolution of starch seals, as well as excessive swelling of the box walls themselves.
Finally, the vast majority of shipping systems do not provide uniform temperatures within the container. For example, one system that is currently used to transport blood samples for laboratory analysis consists of a set of frozen gel packs placed on a shelf at the top of a standard RSC (Rigid Shipping Container) cardboard box. Instrumented tests of this system, however, showed that only the samples immediately below the cooling packs were ever in the specified temperature range of 0 to 10.degree. C.; and furthermore, these samples were in this range for only 8 of the required 24 hour test duration, even at a mild ambient temperature of 22.degree. C. Conversely, samples at the bottom of the box were never in the required temperature range, except for approximately 15 minutes after loading from the storage refrigerator. Less severe, but still significant, uniformity problems were also found to affect other shipping systems. Several of these systems showed extreme temperature inversions of 10.degree. C. or more, typically the result of the placement of cooling media only at the top of the shipping system. Again, samples at the bottom of the box never receive adequate cooling. Also, the common failure of shipping personnel to obey "This Side Up" instructions often leads to inadequate cooling of some of the load.
The consequence of these observed shortcomings of conventional shipping systems is damage to the material being transported. For biomedical materials such as blood, blood products, pharmaceuticals, etc., loss of these products due to heat damage is critical because of the intrinsic financial value of these items and because of the potential health hazards that the use of compromised materials presents. Likewise, heat damage to various foods also presents both financial and health consequences. Finally, the loss of flowers and other expensive, heat-sensitive materials presents serious problems to a variety of industries. Because all of the above industries currently experience substantial shipping losses, the commercial opportunity of the present invention is immense.